Similar experience with me and Lives4Thrills right in front of MakoBobs place, except the Gw was not injured and was feeding. This was only in 6-8 feet of water right off the beach. I had no idea he was behind me until Lives4Thrills shouted out SHARK!
I stayed off the water for about 2 hours then got back in and had a Big dorado swim right next to me as soon as I got about a mile out. Followed by another huge Gw way larger than my 12 ft stealth, 2 different ones in the same day. Needless to say I took it as a sign and stayed out of the water for the rest of the day.